Various types of biometric systems are used more and more in order to provide for increased security for accessing an electronic device, thereby providing an enhanced user convenience. In particular fingerprint sensors have been successfully integrated in such devices, for example, thanks to their small form factor, high performance and user acceptance. Among the various available fingerprint sensing principles (such as capacitive, optical, thermal etc.), capacitive sensing is most commonly used, in particular in applications where size and power consumption are important issues.
Typically, the fingerprint sensor is solely used for providing increased security, for example for unlocking the electronic device. However, it may also be possible to use the fingerprint sensor for controlling the X-Y position of a pointer on a display by detecting motion of ridges and pores of a fingerprint of a user and moving the pointer on the display accordingly.
An example of such a system is disclosed in U.S. Pat. No. 6,408,087, the system being configured to captures successive images of the fingerprint ridges and pores and detects motion in or changes of the ridges and pores based upon the captured successive images. Specifically, successive images are captured by scanning an array of sensors, each of the sensors being smaller than the width of an individual ridge of a fingerprint. Preferably, the array of sensors is smaller than the pad of a finger of a user.
The fingerprint sensing system according to U.S. Pat. No. 6,408,087 provides for an excellent showcase of increased usefulness of a fingerprint sensor by indicating its use in relation to controlling the position of a pointer on a display. However, there appears to be room for further improvement, specifically in relation to simplified operation of the electronic device, at the same time taking into account the desire to improve the overall power consumption of the electronic device.